1. Field of the Invention
The present invention relates to an interpolation frame generating method, an interpolation frame generating apparatus, and a computer program product for generating an interpolation frame which interpolates between two frames.
2. Description of the Related Art
Generally, an image display includes two types such as an impulse type display for continuously emitting only during the persistence time of a phosphor after, an image is written (for example, CRT or field emission type display (FED)), and a hold type display for continuously holding a display of a previous frame until an image is newly written (for example, liquid crystal display (LCD), electro-luminescence display (ELD)).
One of the problems on the hold type display is a blurring phenomenon occurring in moving picture display. The occurrence of blurring phenomenon is causes by the fact that when a moving object is present in an image over several frames and eyes of an observer follow the motion of the moving object, images of the several frames are projected on the retina in an overlapped manner.
Before a displayed image is switched from the previous frame to the next frame, though the image on the same previous frame is being continuously displayed, human eyes predict a display of an image on the next frame and observe it while moving in the moving direction of the moving object on the previous frame image. In other words, since the eye following motion is continuous and sampling finer than the frame interval is performed, human eyes view an image between two adjacent frames, which is observed as blur.
In order to solve this problem, the frame interval of display has only to be shorter. Thus, it is possible to improve unnatural motion in a moving picture having a small number of display frames. As a specific-method, there is considered to utilize motion compensation used in MPEG2 (Moving Picture Experts Group Phase 2) to create interpolation images and to interpolate between adjacent frames.
The motion compensation uses a motion vector detected by block matching. However, since an image is created on block basis in MPEG2, when several objects whose motions are different are contained in a block, correlated portions and non-correlated portions occur, which cause block distortion in the non-correlated portions.
A frame interpolating method for solving such a problem is disclosed (for example, see Japanese Patent Application. Laid-Open No. 2000-224593). One block is divided into several areas and a motion vector is found for each area. Thus, it is possible to reduce block distortion when objects whose motions are different are contained in the block. Further, a motion vector detecting method suitable for dividing a block into areas by a threshold is used and a motion vector detecting method suitable for a pixel block after being divided into areas is used, thereby detecting an optimum motion vector for each area.
The frame interpolating method disclosed in Japanese Patent Application Laid-Open No. 2000-224593 allows the reduction of the deterioration of image quality but cannot calculate a motion vector for an occlusion area accurately.